Thyroid Cancer

Thyroid cancer develops in the cells of the thyroid gland, a butterfly-shaped organ located at the base of your neck. Most thyroid cancers are highly treatable and have excellent prognosis when detected early.

Overview

Thyroid cancer is a disease that occurs when abnormal cells begin to grow in the thyroid gland. The thyroid is an essential endocrine gland that produces hormones regulating metabolism, heart rate, blood pressure, and body temperature. Located just below the Adam's apple, this butterfly-shaped gland plays a crucial role in maintaining many of the body's vital functions.

Thyroid cancer is relatively uncommon compared to other cancers, accounting for about 3-4% of all cancer diagnoses. However, its incidence has been increasing over the past few decades, partly due to improved detection methods. The good news is that most thyroid cancers grow slowly and are highly treatable, especially when caught early. The overall 5-year survival rate for thyroid cancer is approximately 98%, making it one of the most survivable cancers.

There are several types of thyroid cancer, each with different characteristics and prognoses. The most common types include papillary thyroid cancer (about 80% of cases), follicular thyroid cancer (10-15%), medullary thyroid cancer (3-4%), and anaplastic thyroid cancer (1-2%). Additionally, primary thyroid lymphoma and thyroid sarcoma are rare forms. Understanding the specific type is crucial for determining the most appropriate treatment approach and predicting outcomes.

Symptoms

Thyroid cancer often doesn't cause any symptoms in its early stages. As the cancer grows, it may cause various signs and symptoms. Many people discover thyroid cancer incidentally during routine physical examinations or imaging studies performed for other reasons.

Common Symptoms

Less Common Symptoms

Advanced Stage Symptoms

  • Large, firm neck mass that doesn't move
  • Difficulty turning the head
  • Unexplained weight loss
  • Bone pain (if cancer has spread)
  • Respiratory distress

Type-Specific Symptoms

Different types of thyroid cancer may present with specific symptoms:

  • Medullary thyroid cancer: May cause diarrhea, facial flushing, or Cushing's syndrome due to hormone production
  • Anaplastic thyroid cancer: Rapid growth, severe symptoms including difficulty breathing and swallowing
  • Thyroid lymphoma: Rapid enlargement of thyroid, compression symptoms

Causes

The exact cause of thyroid cancer is not fully understood, but it develops when cells in the thyroid undergo genetic changes (mutations) that allow them to grow and multiply rapidly. These abnormal cells lose the ability to die as normal cells would, accumulating to form a tumor.

Genetic Mutations

Several genetic alterations have been identified in thyroid cancer:

  • BRAF mutations: Found in about 45% of papillary thyroid cancers
  • RET/PTC rearrangements: Common in radiation-induced papillary thyroid cancer
  • RAS mutations: Found in follicular and papillary thyroid cancers
  • RET mutations: Associated with hereditary medullary thyroid cancer
  • TP53 mutations: Common in anaplastic thyroid cancer

Environmental Factors

Several environmental factors may contribute to thyroid cancer development:

  • Radiation exposure: The most well-established risk factor, especially in childhood
  • Iodine intake: Both deficiency and excess can influence thyroid cancer risk
  • Previous thyroid disease: Benign thyroid conditions may slightly increase risk
  • Hormonal factors: Estrogen may play a role in the higher incidence in women

Hereditary Factors

Some thyroid cancers have hereditary components:

  • Familial medullary thyroid cancer: Inherited RET mutations
  • Multiple endocrine neoplasia (MEN) syndromes: Type 2A and 2B
  • Familial adenomatous polyposis (FAP): Increased risk of papillary thyroid cancer
  • Cowden syndrome: PTEN mutations increase thyroid cancer risk
  • Carney complex: Associated with follicular thyroid tumors

Risk Factors

Several factors may increase the risk of developing thyroid cancer. Having one or more risk factors doesn't mean you'll definitely develop the disease, but awareness can help with early detection and prevention strategies.

Gender and Age

Thyroid cancer is about 3 times more common in women than men. It can occur at any age but is most common in women in their 40s-50s and men in their 60s-70s. However, when it occurs in children or elderly adults, it tends to be more aggressive.

Radiation Exposure

Previous radiation to the head and neck, especially during childhood, significantly increases risk. This includes medical radiation (radiation therapy), nuclear accidents, and atomic bomb radiation. Risk increases with dose and decreases with age at exposure.

Family History

Having a first-degree relative with thyroid cancer increases your risk by 3-6 fold. About 5% of thyroid cancers are hereditary. Familial syndromes like MEN 2, familial medullary thyroid cancer, and familial papillary thyroid cancer significantly increase risk.

Benign Thyroid Disease

Previous benign thyroid conditions such as thyroid nodules, goiter, or thyroiditis may slightly increase risk, though most benign conditions don't become cancerous.

Iodine Intake

Geographic regions with iodine deficiency have higher rates of follicular and anaplastic thyroid cancers, while areas with adequate iodine have more papillary thyroid cancers.

Obesity

Studies suggest that obesity may increase thyroid cancer risk, possibly due to hormonal changes, increased TSH levels, or insulin resistance.

Diagnosis

Diagnosing thyroid cancer typically involves a combination of physical examination, imaging studies, laboratory tests, and tissue sampling. Early and accurate diagnosis is crucial for determining the appropriate treatment strategy.

Physical Examination

  • Palpation of the thyroid gland and neck lymph nodes
  • Assessment of thyroid nodule characteristics (size, firmness, mobility)
  • Evaluation of voice changes or hoarseness
  • Examination for signs of hormone overproduction

Imaging Studies

Ultrasound

First-line imaging for thyroid nodules. Identifies suspicious features like microcalcifications, irregular borders, and increased vascularity. Also guides fine-needle aspiration.

CT or MRI Scan

Used to evaluate extent of disease, especially for large tumors or suspected spread to nearby structures. Avoided before radioiodine therapy.

Radioiodine Scan

Determines if thyroid nodules are "hot" (functioning) or "cold" (non-functioning). Cold nodules have higher cancer risk.

PET Scan

Used for aggressive thyroid cancers or when looking for metastatic disease, especially in radioiodine-resistant cases.

Laboratory Tests

  • Thyroid Function Tests (TSH, T3, T4): Usually normal in thyroid cancer
  • Thyroglobulin: Tumor marker for differentiated thyroid cancer follow-up
  • Calcitonin: Elevated in medullary thyroid cancer
  • CEA: May be elevated in medullary thyroid cancer
  • Genetic testing: For hereditary forms (RET mutations)

Fine-Needle Aspiration (FNA) Biopsy

The gold standard for evaluating thyroid nodules:

  • Ultrasound-guided needle biopsy of suspicious nodules
  • Cytological examination classifies results using Bethesda System
  • Categories range from benign to malignant
  • Molecular testing may help clarify indeterminate results

Molecular Testing

Advanced genetic tests for indeterminate FNA results:

  • Gene expression classifiers (Afirma, ThyroSeq)
  • Mutation panels (BRAF, RAS, RET/PTC)
  • MicroRNA classifiers
  • Help avoid unnecessary surgery

Treatment Options

Treatment for thyroid cancer depends on the type and stage of cancer, overall health, and personal preferences. Most thyroid cancers are highly treatable, and many patients are cured with initial therapy.

Surgery

Total Thyroidectomy

Complete removal of the thyroid gland. Most common surgery for thyroid cancer. Requires lifelong thyroid hormone replacement. Allows for radioiodine therapy and thyroglobulin monitoring.

Lobectomy (Hemithyroidectomy)

Removal of one thyroid lobe. Option for small, low-risk papillary cancers. May not require hormone replacement if remaining lobe functions normally.

Lymph Node Dissection

Removal of neck lymph nodes if cancer has spread. Central neck dissection common. Lateral neck dissection for lateral node involvement.

Radioactive Iodine Therapy

  • Uses radioactive iodine (I-131) to destroy remaining thyroid tissue
  • Effective for papillary and follicular thyroid cancers
  • Given as outpatient pill or liquid
  • Requires low-iodine diet preparation
  • Not effective for medullary or anaplastic thyroid cancer

Thyroid Hormone Therapy

  • Daily levothyroxine pills replace normal thyroid hormone
  • Suppresses TSH to prevent cancer recurrence
  • Dose adjusted based on cancer risk and TSH goals
  • Regular monitoring required

External Beam Radiation

  • Used for cancers that don't take up radioiodine
  • Palliative treatment for bone metastases
  • May help control locally advanced disease
  • Typically given over several weeks

Targeted Drug Therapy

Tyrosine Kinase Inhibitors

Lenvatinib, Sorafenib - For advanced differentiated thyroid cancer

Vandetanib, Cabozantinib - For medullary thyroid cancer

BRAF/MEK Inhibitors

Dabrafenib + Trametinib - For BRAF-mutant anaplastic thyroid cancer

RET Inhibitors

Selpercatinib, Pralsetinib - For RET-altered thyroid cancers

Chemotherapy

  • Limited role in most thyroid cancers
  • May be used for anaplastic thyroid cancer
  • Sometimes combined with radiation therapy
  • Doxorubicin most commonly used agent

Follow-up Care

  • Regular thyroglobulin and anti-thyroglobulin antibody testing
  • Neck ultrasound examinations
  • Whole body radioiodine scans when indicated
  • TSH suppression monitoring
  • Long-term surveillance for recurrence

Prevention

While most cases of thyroid cancer cannot be prevented, certain measures may help reduce risk or enable early detection:

Primary Prevention

  • Radiation Protection: Minimize unnecessary radiation exposure, especially in children
  • Prophylactic Surgery: For high-risk hereditary syndromes (MEN 2, familial medullary thyroid cancer)
  • Potassium Iodide: Protection during nuclear accidents for those near radiation exposure
  • Maintain Healthy Weight: Obesity may increase thyroid cancer risk

Screening Recommendations

  • General Population: Routine screening not recommended
  • High-Risk Individuals:
    • Annual thyroid examination for radiation exposure history
    • Genetic testing and screening for hereditary syndromes
    • Ultrasound screening for familial thyroid cancer
  • Genetic Counseling: For families with hereditary thyroid cancer syndromes

Early Detection Strategies

  • Regular self-examination of the neck
  • Prompt evaluation of thyroid nodules
  • Awareness of symptoms and risk factors
  • Regular check-ups if you have risk factors

When to See a Doctor

Early detection of thyroid cancer significantly improves treatment outcomes. Seek medical attention if you experience any concerning symptoms or have risk factors for thyroid cancer.

Immediate Medical Attention

  • Rapidly growing neck mass
  • Difficulty breathing or swallowing
  • Hoarseness or voice changes lasting more than 2 weeks
  • Neck mass with difficulty turning head

Schedule an Appointment

  • Discovery of a lump or swelling in your neck
  • Persistent neck or throat pain
  • Swollen lymph nodes that don't resolve
  • Family history of thyroid cancer
  • Previous radiation exposure to head/neck
  • Known thyroid nodules that are changing

Risk-Based Screening

Consider regular screening if you have:

  • History of childhood head/neck radiation
  • Family history of medullary thyroid cancer
  • Known genetic syndromes (MEN 2, FAP, Cowden)
  • Multiple family members with thyroid cancer

Related Conditions

Other Thyroid Conditions

Related Cancers

Related Symptoms

References

  1. Haugen BR, et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016;26(1):1-133.
  2. National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Thyroid Carcinoma. Version 2.2023.
  3. Cabanillas ME, McFadden DG, Durante C. Thyroid cancer. Lancet. 2016;388(10061):2783-2795.
  4. Wells SA Jr, et al. Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma. Thyroid. 2015;25(6):567-610.
  5. Filetti S, et al. Thyroid cancer: ESMO Clinical Practice Guidelines. Ann Oncol. 2019;30(12):1856-1883.

Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.